1. Field of the Invention
The present invention generally relates to an electronic apparatus such as a portable telecommunication apparatus and, more particularly, to an electronic apparatus including circuitry blocks mounted on upper and lower surfaces of a circuit board and a shield structure shielding the circuitry blocks against electromagnetic wave radiation from one or more other apparatus and/or shielding one or more apparatus against electromagnetic wave radiation from the electronic apparatus.
2. Description of the Related Art
An electronic apparatus includes electronic components which often generate electromagnetic signals. The signals may radiate to and interfere with the operation of other apparatus. Further, the electronic apparatus may receive electromagnetic signals which are generated by the other apparatus causing interference with the operation of the electronic apparatus. To reduce such interference, electrically conducting material may be provided in the electronic apparatus between the electronic components of the electronic apparatus and the other apparatus. The electrically conducting material functions as a shield structure.
It is desirable to have an easily removable shield structure if a service person wishes to interchange the components in the electronic apparatus. Various structures have been developed to accomplish this purpose.
One type of conventional shield structure is depicted in FIGS. 7 and 8. Referring to FIGS. 7 and 8, reference numeral 1 designates a double-sided circuit board having upper and lower surfaces. Electronic components (not shown) are mounted on each surface. Additionally, a ground 1a is printed on each surface.
Shield cases 2 and 3, each made of a conductive material, are designed to mate against circuit board 1. Shield case 3 has a protruding portion 3a fitted with a conductive spring 5. Shield case 3 is mounted against the lower surface of circuit board 1 by urging conductive spring 5 toward lower ground 1a using a fitting such as a screw (not shown). Conductive spring 5 contacts lower ground 1a as a result of the elasticity of conductive spring 5. In this manner, shield case 3 is electrically coupled to lower ground 1a through conductive spring 5. Shield case 3 then shields the electronic components mounted on the lower surface of circuit board 1 against electromagnetic radiation from other electronic apparatus.
Shield case 2, having essentially the same structure as shield case 3, is attached to the upper surface of circuit board 1 in the same manner as shield case 3 is attached to the lower surface of circuit board 1. Shield case 2 then shields the electronic components mounted on the upper surface of circuit board 1 against electromagnetic radiation from other electronic apparatus.
Since each spring 5 is required to attach to both shield case 2 and shield case 3, a spring 5 is required for each of shield cases 2 and 3. As a result, an increased number of springs 5 is required for the structure depicted in FIGS. 7 and 8. Further, it is troublesome to attach each spring 5 to its shield case 2 or 3.
FIGS. 9 and 10 show another conventional shield structure. For the structure of FIGS. 9 and 10, a U-shaped double-cantilever spring 7 is soldered in electrical contact to each of the grounds 1a of circuit board 1. Each spring 7 includes a pair of opposing clamping portions 7a. A protruding portion 2a from shield case 2 and a protruding portion 3a from shield case 3 are each inserted into corresponding pairs of clamping portions 7a. As a result, protruding portion 2a is clamped by clamping portions 7a of upper channel 7 and protruding portion 3a is clamped by clamping portions 7a of lower channel 7, due to the elasticity of the clamping portions. In this manner, each of shield cases 2 and 3 is attached to one of the surfaces of circuit board 1 and electrically coupled to one of the grounds 1a, as shown in FIG. 9. As a result, the electronic components mounted on each surface of circuit board 1 are shielded against electromagnetic radiation from other electronic apparatus by shield cases 2 and 3.
A disadvantage associated with the structure depicted in FIGS. 9 and 10 is that a U-shaped spring 7 must be attached to each surface of circuit board 1. As a result, an increased number of U-shaped springs 7 is required for the structure shown in FIGS. 9 and 10. Further, it is troublesome to attach each U-shaped spring 7 to each surface of circuit board 1.